Microscopic examination of thin sections

Optical examination of thin ceramic sections is generally performed by methods of transmission microscopy. The primary methods of examination include bright field, polarization, phase-contrast, and interference microscopy. 

In the bright field method, the amplitude of the transmitted light is changed by the differences in optical absorptivity between the microstructural components. This results in the creation of darker and brighter regions (i.e., high-contrast object structures) in the image. 

Polarization is applied to anisotropic objects. The non-cubic components exhibit optical birefringence between two crossed polarizers. In other words, there is a periodic cycle of cancellation (destructive interference) and intensification (constructive interference). This effect can be measured and is used to identify the various components. 

Phases can also be identified by means of interference microscopy combined with a precise determination of the indices of refraction. 

141 and 142 show two examples of thin-section images from the field of rocks and minerals. More detailed and extensive information can be obtained from publications by Rigby (1953), Beyer (1977), Freund, Gugel, and Willmann (1978) (see literature references). 

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Table IV. Checklist for rapid syslenialic petrographic microscopic examination of thin. sections (modihed from Milner. 1962a. and Walstrom. I%U).

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